DE2315794A1 - SAVING DISPLAY EAR - Google Patents

Description

Büblinoen, March 22, 1973 ker-aa

Applicant: International Business Machines

Corporation, Arraonk, N.Y. 1O5O4

Official file number: New registration File number of the applicant: YO 971 070

Saving display tube

The invention relates to a storing cathode ray tube for display purposes. - It becomes a bistable storage indicator tube described with an electroluminescent layer, on its inner surface with an electron beam gun applied information can be stored. With the help of the electron beam gun, the potential of the inner Surface of the electroluminescent layer in the to be switched on Districts brought to the potential of a designated collector electrode. An alternating voltage signal becomes the effect on the electroluminescent layer by one on their applied transparent conductive layer on the outer surface, with an alternating field in the switched on Districts with the formation of luminescence occurs.

This is the case with conventional bistable two-beam tubes Their characteristic is their low brightness. E.g. offers a typical two-beam height with utilization of the cathodoluminescent Effect a too low brightness with long storage viewing times. In order to be bistable with such cathodoluminescent Tubes to achieve sufficient functional stability ^ must can be used with relatively low DC voltages in order to be able to use On the other hand, to achieve sufficient brightness for such tubes, high beam intensities have to be used. Because of the

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The peculiarity of the light generating mechanism inherent in cathodoluminescence leads to relatively high beam intensities for generating sufficient brightness on the other hand, to a short life of the kothodoluminescent material. Therefore, the technique known storage and display devices, ^J have, in particular those based on the cathodoluminescent effect, low brightness and short life according to the state. Regarding the state of the art, please refer to the publication in the IBM Technical Disclosure Bulletin, Vol. 13, No. 9 February 1971, page 2513.

The object of the present invention is to provide a bistable storage and display tube with increased brightness and improved service life compared to the prior art; alternatively, it should only be possible to save or save with displays; the brightness should be adjustable and both the electroluminescence as well as the cathodoluminescence exploited will. - ·

The solution to this problem is characterized in claim 1. Advantageous refinements are described in the subclaims.

An embodiment of the invention is explained with reference to the drawings and the following text.

Show it:

Fig. 1 shows a section through the bistable memory and

Display tube according to the present invention and

Fig. 2 shows the course of the secondary electron yield in

chosen electroluminescent display material depending on the electron energy used.

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The overall arrangement shown in FIG. 1 corresponds to the types of games known Cathode ray tubes. Conventional two-beam storage tubes sineUin. built this way. With conventional However, the layer is made up of cathodoluminescent spider tubes 1 made of cathodoluminescent material, whereas in the embodiment according to the present invention the material of the layer 1 is electroluminescent. In addition, the jAnor ^ ung ^ acc Fig. 1 compared to conventional cathodoluminescent storage tubes fine-tune. Grid collector 3 in front of layer 1 and one Anode 5 behind it. An alternating voltage from an alternating voltage source 7 is fed to this anode 5. More details in addition, a description will be given of, in particular, a mode of operation that was previously not known in the case of storage tubes.

The storage tube 9 itself can correspond to conventional storage tubes in terms of tube material and construction. For example, the tube 9 can be made from Made of glass. The high energy electron beam gun indicated at 11 is also said to be of a known type be. The electron source 13 is used to emit electrons through a focusing device 15 to the perpendicular and horizontal ones generated by deflection electrodes 17, 19 and 21 Deflection fields. The electrodes 17 and 19 are used for vertical Deflection of the electron beam, whereas the electrode 21 and its partner not visible behind it to the horizontal Serve as a distraction.

According to conventional designs, electron guns flood 23 and 25 by associated focusing devices 27 and 29 through the entire surface of the electroluminescent layer 1 with electrons of relatively low energy. The emitters 23 and are connected to the negative pole of voltage sources 31 and 33, whereas the surface of the layer 1 is grounded via the collector 3. In the usual way, the electron source 13 is for High energy electrons with. the negative pole of a voltage source 35 connected, the positive pole of which is on the other hand grounded. As an example of such a high-energy electron source, a

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Source 13 at - 2 kV. The voltage sources 31 and 33 may give e.g. -300 V. However, the voltage values given are only examples; they can range from 100 up to a few 100 V.

The collector 3 is, as already mentioned, grounded and serves as a collector for secondary electrons which are reflected back by the electroluminescent layer 1. On the other hand, this collector can also be designed in a different shape, for example as a ring, and can also be at a different potential which is sufficiently positive with respect to the other active parts of the tube . -.- ■; ■■■;

The electroluminescent layer 1 can be made of any known electroluminescent material, e.g. electroluminescent phosphoritescent in powdered form in an inorganic dielectric binder. For example, copper-doped zinc sulfide can be used in a glass binder. More appropriate Prior art is given in U.S. Patent 3,313,652. An alternative embodiment can consist in that the electroluminescent layer with another layer of high secondary electron yield is covered.

According to the display object of the present invention, the conductive anode 5 as shown in FIG. 1 must be transparent. In addition For example, known transparent conductor materials can be used such as the oxides of tin, indium or copper or thinly etched ones other metal layers. For example, a layer of copper iodide could also be used. When manufacturing can either the electroluminescent layer 1 on the layer of the anode 5 or vice versa. After applying the layers 1 and 5 in the tube 9, the tube is covered with a transparent one Layer 37 sealed, which for example consists of relatively thick glass.

In contrast to cathodoluminescent material, the light when

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Emits electron bombardment on its surface, electroluminescent material generates light under the influence of an alternating voltage field acting through it. When planning to selectively act on certain areas of electroluminescent material such alternating fields for display purposes, some difficulties arise. According to the present invention, the alternating field is brought into effect only in selected areas of the electroluminescent layer 1 when it is to be stored and displayed. For this purpose, the secondary emission properties of the electroluminescent material and the effects of the electron guns according to FIG. 1 are used. For this purpose, the alternating voltage source 7, which is also _{denoted by V p} , allows an alternating field to act through the electroluminescent layer 1 in the areas in which the writing gun 11 has applied charges in accordance with the information to be stored and possibly displayed. Thus, visible light is always generated when the alternating electrical field acts through the layer 1. For explanation, all the regions of the luminescent layer 1 in which the light generation condition corresponding to the writing of charge is established should be regarded as being turned on. The uncharged districts, on the other hand, should be designated as disabled. Alternating fields through the luminescent layer 1 are then generated in the switched-on areas in that the charged surface areas are connected to the potential of the grid collector 3 by ejected secondary electrons. ^{The areas of} the electroluminescent layer 1 that are uncharged, v / ground not acted upon by electrons from the electron beam learn; they have no animal field. under the influence of the AC voltage source 7. The task of the direct voltage source (V) is to bias the electroluminescent layer 1 in order to avoid undesired leakage currents. By means of the direct voltage source 39, an operating point for the layer 1 is selected so that no breakdowns occur with the applied alternating potentials.

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- D ~ '

Fig. 2 shows the typical electron emission yield as a function of the electron energy in conventional electroluminescent phosphoritescenters. The horizontal straight line through the characteristic curve corresponds to δ = 1, where δ is the yield ratio of returning electrons to primary electrons applied to the material. Two types of electrons are emitted back; on the one hand, real secondary electrons and, in addition, thrown back or reflected primary electrons. When the electron energy is zero or negative, which corresponds to the area on the left of the ordinate, δ = 1. This means that all electrons that penetrate into the vicinity of the material under consideration do not have enough energy to generate secondary electrons in it; they are only thrown back or reflected at a 1: 1 ratio. This corresponds to a state of equilibrium and is denoted _{in FIG. 2 by V "A1.} When the electron energy of V _E q. is made larger starting out, the yield δ decreases. This decrease means that more electrons are sent into the electroluminescent material than come out. This means that the material takes on a charge. At V ₀₀₁ the yield becomes 1 again, and beyond that it can be seen that more electrons come out of the material than are put into it. This point is unstable because any change in electron energy either has a tendency towards V__. or after V "_ causes. The dashed line, which starts from the culmination point of the characteristic between V ₀ and V__, “represents the normal decrease in the yield that would occur with a further increase in the electron energy. At V " _CR 2 there is again a yield δ = 1. The solid curve through V- results from the influence of the grid collector 3 next to the electroluminescent" layer 1. Setting the grid collector 3 to the corresponding potential changes the yield curve and the achievement of a point of equilibrium

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In order to achieve a good secondary emission yield with the electroluminescent material of the layer 1, the electrons must reach the layer material with an energy in the range between V ^ _n and V ^ ₀ . In order to achieve a constant equilibrium in the electron energy range under consideration according to the basic idea of the present invention, the grid collector 3 is attached close to the electroluminescent layer 1 and connected to a less negative potential. When operating an arrangement according to FIG. 1, it should be assumed that initially no charges are present on layer 1. This does not correspond to any applied information. No electrons are attracted by the electron guns 23 and 25 to the surface of the electroluminescent material. Thus, no secondary emission is generated either and 6 = 1 as described. This state corresponds to the equilibrium point V _Q according to FIG applied · potential to go along. The potential of the inner surface IA of the layer 1 thus follows the potential of the AC voltage source 7, which is connected to the anode 5. This means that there is no alternating field through the electroluminescent material.

A little further you can see that after leaving of the equilibrium point V__. of the electroluminescent material the AC voltage source 7 begins to act on the characteristic curve according to FIG. Seek during the first positive half-source Electrons from the emitters 23 and 25 to penetrate into the electroluminescent material of the layer 1, with correspondingly the characteristic curve δ decreases. Since the electroluminescent material of layer 1 is basically to be regarded as a dielectric, this takes up charge and accumulates it during all subsequent positive half-waves. This results in some self-biasing effect, although after some agreement

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Alternating voltage cycles sets a negative tension bias, that of the peak value of the AC voltage signal applied to layer 1 is equivalent to. With this self-biasing generated, the alternating field fluctuates between zero and a negative potential. According to the characteristic, δ is in the negative energy range 1 and no secondary electrons escape.

In order to achieve the switched-on state in selected areas of the electroluminescent material of the layer 1, the electron gun 11 is used and, with its help, a desired arrangement of charges is applied to the inner surface IA of the layer 1. Any desired charge arrangements, for example in the form of alphanumeric characters, can be applied. As soon as corresponding charge images are present on the layer 1 ″, the corresponding charges attract electrons from the electron guns 23 and 25. These attracted electrons in turn generate a secondary electron emission which is collected by the grid collector 3 Font the electroluminescent material in the state of equilibrium V _Λ _

"'EQ2

according to FIG. 2. The effect of the grid collector 3 on the back-emitted Electrons is the connection of the charged areas on the surface IA with earth. Correspondingly for areas that are grounded in this way of the charge pattern applied, the alternating voltage source 7 can now build up an alternating field in these areas. Electroluminescence is effective in the corresponding areas and a visible image is generated.

The electron guns 23 and 25 are thus used to charge-inscribed the surface IA of the electroluminescent layer 1 Districts to connect to earth, the alternating voltage applied to the anode 5 through the electroluminescent Material through an alternating field and thus can generate luminescence. In the districts of the area IA without registered charges the area in the potential can freely match the fluctuating potential

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the AC voltage source 7 run along. These named districts are in the off state. As already stated, the writing gun 11 produces a beam of much higher energy and Density than the electron guns 23 and 25. Under the influence of the writing gun 11, target areas become more energy-positive Area between the first intersection point V and V_ _ according to FIG. 2 offset. This higher energy is retained even if the alternating voltage acts on the anode 5 as long as the following Condition is met:

J ' _f = | <i-6> | J _f > c _EL v _Bp

Here, J ' _{f is} the surface electron radiation on the switched-on areas, J _{f is} the electron beam density of the electron beam, C "_ is the capacitance per unit area of the electroluminescent layer and V is the anode potential of the anode 5, the point above V marking the time dependence.

In the selected embodiment, J 'can be greater than CV _, _. under the following parameters and conditions:

Umbrella area == 8 χ 10 cm

Dielectric constant = 2ε thickness of the phosphorescent = 75 pm V _ßp = 200 sin 2 irx 500 χ t electron beam current = 2 mA

This results in:

j = = 0.025 mA / cm ^{2 r} 80 a

With δ-l approximately equal to 1, if the applied energy is smaller

is as V ^,. ,,, results
üyz

^2ε 0 2

= - j 200 χ 2π χ 500 = 0.0148 mA / cm

3x25xlO ~ *

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and thus

^J 'f > BP:

The alternating voltage source 7 was previously known as with the anode 5 considered connected. Of course, the anode 5 can also be kept at a fixed potential and the grid collector 3 with the AC voltage source to generate the required alternating field be fed.

It should be noted that in addition to the electroluminescence achieved In the selected areas of layer 1, a certain cathodoluminescence can also be achieved in these areas. Many electroluminescent materials give cathodoluminescence at the same time. Generate when using such materials in addition to electroluminescence due to the alternating field of The electrons coming from the electron guns, which are attracted to the described areas, also have a certain amount of Cathodoluminescence. Optionally, a thin layer of cathodoluminescent material can also be applied to the inner surface IA the layer 1 are applied, with which both electroluminescence and cathodoluminescence can be generated.

It should also be noted that the principles of the present Invention, according to which areas to be selected are switched through to a given potential on a display area, in order to be able to bring an alternating field to training other than electroluminescent display surfaces can be used. For example, instead of layer 1, an arrangement can be used by liquid crystal cells or gas discharge cells. With such a design, the inner surface would be the Display area based on IA according to FIG. 1 with one layer Provide secondary electron donating material in a dielectric binder. Charges could be in the form of a picture or Writing pattern on the secondary emission material in a similar manner

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Be applied as described above. Then were after the application of the charge pattern of the electron flow from the electron guns to the secondary emission material and the as a result of this, secondary electrons emerging and collected by the collector serve as a connection to the inner surface of the liquid crystals or gas cells. Corresponding an alternating field acting through it could be developed to produce a visual indication. Other trainings from Display mechanisms could also be used.

It is significant that, according to the present invention, relatively large radiation densities for the one-time application of the charge pattern are only required for a short time, so that the material service life is not significantly affected in spite of high charge densities. On the other hand, the proposed solution offers a relatively high display brightness with a long service life.

However, despite the benefits of the present invention, any electroluminescent material has a finite life. In order not to always have to replace the entire tube when replacing the electroluminescent material, it seems advantageous to the inner coating of the tube corresponding to the layer 1 according to FIG. 1 only as a secondary electron-emitting material in a dielectric binder. The electroluminescent Layer itself with an overlying transparent anode surface on the outer surface of the glass face 37 of the tube. The anode 5 inside would be omitted and a point-to-point connection between the secondary electron-emitting one Layer and the now outer electroluminescent layer with a through the glass face 37 provided through an arrangement of grommet pins. Such a design would be analogous to the metal door arrangement, which have already been published in the IBM Technical Disclosure Bulletin, Vol. 12, Wo. 12 May 1970, page 2324.

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Claims (15)

PATEN TA N S P RÜ CHE Storing cathode ray ^{tube, etc.} for display purposes, characterized by the combination of the following features: a) Display area that is used for storage by means of an electron beam charge pattern applied to its inside (IA) and for the formation of electroluminescence on its outside by means of an alternating electric field the charge pattern applied to the inside (IA) is suitable. b) electron beam gun (11) for labeling said Inside (IA) of the display area with electrically storable Charge samples in a pictorial or written arrangement. c) Anode (5) for applying an AC voltage signal the display area for generating a penetrating Alternating field. d) Collector (3) for switching through the charge-labeled areas by means of secondary electrons emerging from the inside (IA) of the display surface under constant electron irradiation to a predetermined potential (earth), the constant electron irradiation with a radiation intensity that is significantly lower than the radiation intensity of the electron beam gun (11) and the predetermined potential (earth) , to which it is switched through, is dimensioned such that the alternating field which forms at the charge-labeled areas generates visible light, whereas the areas on the inside (IA) of the display area that are not charge-labeled do not reach the predetermined potential (Earth) and oscillate freely with the applied alternating voltage signal without emitting light. YO 971 070 30 9881/0757 2. The tube of claim 1, wherein the applied AC voltage signal can optionally be switched on / off, so that if the data is saved, a visible time can be selected Display is feasible. 3. Tube according to one of the preceding claims, characterized by a dielectric coating of the display surface that emits secondary electrons when electrons hit previously electrically charged areas. 4. Tube according to one of the preceding claims, characterized by a display surface made of electroluminescent Material for emitting visible light in the areas selected by the cargo labeling. 5. Tube according to one of the preceding claims, characterized in that that the display surface on its outside as an anode (5) is a support of a transparent having electrically conductive material. 6. Tube according to one of the preceding claims, characterized in that that the collector (3) for switching through the areas labeled by charge is spatially close to the charge storage unit Inside (IA) of the display area is arranged and that for constant electron irradiation of the precharged, secondary electron-emitting inside (IA) at least an additional, continuously emitting electron gun (23, 25) with opposite the radiation intensity the electron beam gun (11) much less Radiation intensity is provided, which is not sufficient for the application of itself Charge patterns on the inside (IA) of the display area, but for the formation of secondary electron emission in YO 971 070 309881/0757 by the electron beam gun (11) preceding with Charge labeled districts is sufficient. 7. Tube according to one of the preceding claims, characterized in that in the charge-labeled areas the display area next to the electroluminescence one of these supporting cathodoluminescence occurs. 8. Tube according to one of the preceding claims, characterized characterized in that in addition to the applied AC voltage signal DC bias to suppress undesired leakage currents in uncharged areas is provided. 9. Tube according to one of the preceding claims, characterized in that the AC voltage signal between the anode (5) and the collector (3) is applied. 10. Tube according to claim 9, characterized in that one pole of the AC voltage signal source (7) with the anode (5) is connected. 11. Tube according to claim 9, characterized in that one pole of the alternating voltage signal source (7) with the Collector (3) is connected. 12. Tube according to one of the preceding claims, characterized characterized in that the collector (3) for switching through the areas labeled with charge to the predetermined potential (earth or earth in series with the AC voltage signal source 7) as a conductive grid formed on the inside (IA) of the display surface is. YO 971 070 309881/0757 13. Tube according to one of the preceding claims, characterized characterized in that the electroluminescent display surface is arranged as a layer (1) within the tubular bulb (9) is. 14. Tube according to claim 13, characterized in that the electroluminescent layer (1) on its inside (IA) has a coating with secondary electron emittable particles in a dielectric binder. 15. Tube according to one of claims 1 to 12, characterized in that that two separate layers are provided for the display area, a chargeable inner layer (I) _7, the secondary electrons are designed to be emissive and arranged within the tubular piston (9), and an electroluminescent outer layer with overlying transparent anode (5), which together on the outer End face (37) of the tubular piston (9) are arranged interchangeably, with electrically conductive point-to-point connections are provided between the inner and outer layers. YO 971 070 309881/0757 Blank page